Microwave transmission system



April 1947. H. w. KLINE MICROWAVE TRANSMISSION SYSTEM Original Filed May 28, 1943 Inventor":

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Patented Apr. 8, 1947 UNITED STATES PATENT OFFICE MICROWAVE TRANSMISSION SYSTEM Halsey W. Kline, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York 3 Claims. (Cl. 178-44) My present invention is a division of my copending application, Serial No. 488,824, filed May 28, 19413, and it has for its object to provide a new and improved tuning arrangement for a microwave transmission, system.

My invention relates more particularly to a systerm for transmitting microwave energy from a resonating body to an output circuit. For transmitting high frequency energy from an scillator of the resonant cavity type to an output circuit, such as an antenna or the radiating stub of a wave guide, it is desirable to employ a transmission line of the concentric conductor type both for flexibility and ease of tuning over a wide band of frequencies and for simplicity of connection impedance matching.

A further object of my invention isto provide an improved means for easily and rapidly adjusting the length of a concentric transmission line.

The features of ray invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself, however, both as to its organizat on and method of operation, together with further objects and advanthereof, best 1, e understood by reference to the following description taken in connection with the accompanying drawing, in which Fig. 1 shows a high frequency transmission system according to my invention; 2 is a View, partly in section, of a rotary tuning device used in the system of Fig. 1; Fig. 3 a side view, partly in section, of the device of Fig. 2 along the lines 3--3; Fig. 4 is an enlarged view of the contacting means employed in the tuning device of Fig. 3 taken along the lines l l; and Fig. 5 is a side view along the lines 55 of Fig. 4.

Referring to 1, I have shown a high frequency transmission system in which high frequency energy within the cavity resonator Ill is supplied to an output radiating element H over pair of transmission lines l2, IS. The cavity resonator Ill may be associated with any desirable high frequency oscillator operating to produce oscillations having a very small wave length, for example, of the order of 18 centimeters, The transmission line i2 is of the concentric type having a tubular outer conductor and a centrally disposed inner conductor. The line l2 at its point of connection with the cavity resonator I0 is provided with a coupling loop l5 extending within the resonator l8 and is provided at its junction with transmission line l3 with a similar coupling loop l5.

The output radiator ll, which maybe for example an antenna element or a radiating stub projecting into a wave, uide, is iormcdbv n .e tension of the inner conductor ll of concentric transm ssion line Conductor l! is provided with a loop portion l8 adjacent the coupling loop 16 at the end of line 12. The loops [6, l8 preferably are one-turn coils and are tightly coupled together. The lower end of line i3 is connected to a rotary tuning device 2b which provides means for adjustably connecting a short-circuiting element 2! between the inner and outer conductors of a substantially circular extension of the transmission line 3. The slider 2% shorts the inner conductor of this extension of line to the grounded outer conductor and provides means for allowing the electrical length of the entire antenna output circuit to be adjusted to resonate at the frequency of the cavity resonator. When the output circuit of the system is adjusted to resonate at the frequency of the cavity resonator, the coupling loops l6, l8 enable opt mum loading of the high frequency source or resonant cavity l3.

Referring to Fig. 2, I ave shown the tuning device in preferred As shown, the device 26 comprises a stationary body member 23 in the form of a circular piece of metal having a substantially circular groove on its right hand face. The body member has a centrally located bearing surface for rotor-ably supporting a cooperating bearin surface 25 on a rotatable body membe The body member similarly is shown e. metallic plate having a circular groove Z'l formed on its left hand surface in such a ianner that the groove 21 lies adjacent the groove 23 to form therewith, when the members 22 and 26 pressed together, a circu" lar passage through the compo .te tuning device 25. This passage, moreover, is circular in cross section and a substantially complete loop of rigid wire 29 is supported in the center of the circular passageway formed ill the device 20, As thus described, the wire as a d grooves and 21 in body members form a section of concentric transmission line. The body member 222 is provided with a shoulder and rotatable body member 25 is provided with a flanged portion 32 wh ch fits about the shoulder 3i. Member 26 is provided with a hub portion 33 in which one end of a shaft 3 4 is secured by means of a screw lhe shaft 3d carries its other end a knurled adjusting knob 35. An extension of the cooperating bearing surface 25 is threaded and a nut 38 threaded thereon bears against a washer 3d and a spring member id to hold the body members $32 and Z5 pressed together with suliicient force that good contact between adjacent surfaces of the body members is secured, but that movable member 23 may be easily rotate-d with respect to the stationary member 22 by turning the knurled knob 3b. Screws 3% provide means for affixing stationary body member 22 to a supporting object. I

The Wire 29 is provided with a connecting portion 32 which extends at right angles to the plane of the loop of wire lying in the grooves 23 and 2?. A plug 43 of any suitable insulating material, such as polystyrene, both insulates the wire 42 and the loop 29 from the member 22 and supports one end of the loop in a fixed position such that the loop lies substantially i the plane of adjacent surfaces of members 22 and 2B. The opposite end of the loop of wire is electrically conducted, as by soldering, to a circular metal connection ring 4 (as shown in Fig. 3). The diameter of the circular ring 44 is the same as the diameter of the circular passageway formed by the grooves 23 and 2'! and this ring 44 is soldered to member 22 so that one end of the loop of wire '29 is grounded to the body member 22.

The sliding contact for adjusting the length of the transmission line between the connection portion 42 and the base member 22 is shown in Figs. 4 and 5. This sliding contact comprises a cylinder 46, a piston 47 and a contact member 49. The cylinder 46 is located in a hole drilled in the movable member 26 and is formed with a semi-circular bearing portion 49 at its lower end, the bearing portion 49 sliding in the groove 23 formed in the body member 22. The spring member 48 which lies between the bearing surface 49 and conductor 29, carries a plurality of arms 50 for contacting the conductor 29. A retaining member which is fastened to the rotatable member 26 by means of screw 52 has a pair of openings 53 for engaging fingers 54 at the upper end of cylinder 46. Spring 55 of any suitable material compressed between retaining member 51 and the piston 46 provides means for assuring contact between conductor 29 and the grounded. member 26.

Secured to the rotatable member 29 along its outer periphery by means of screw 51 is a stop member 58. A stop pin 59, secured to the stationary body member 22 operates in conjunction with stop member 58 to limit the rotation of movable member 26 with respect to fixed member 22.

In the operation of the tuning device 20, as the knurled knob 39 is turned to adjust the position of contact 59 on conductor 29, the length of line l3 may be adjusted to a desired value. piston 41', biased against conductor 29 by means of spring 55, assures positive contact of spring 50 against conductor 29 to ground the conductor at this point. In this way the device 29 provides a compact, variable-length concentric line turning device which may be used to vary the length of line 13 in Fig. 1 and to adjust the tuning of the output circuit. Since the coiled conductor 29 and the walls of the grooves 23 and 21 cooperate to form an extension of transmission line [3 which has the same impedance characteristics of line 13, all difiiculty of terminating line I3 is eliminated. The construction is such that all backlash is avoided and adjustment of the length of line l3 may be made easily and rapidly. Moreover, when used in conjunction with the link coupling line l2, adjustments of the length of line [3 by means of tuning device 20 have substantially optimum loading effect on the cavity resonator ill. The link coupling line 12 to a large extent is independent of frequency and provides not only improved coupling between resonator l0 and the radiating element H, but also permits optimum tuning of the output circuit of the system.

While I have shown a particular embodiment of my invention, it will of course be understood that I do not wish to be limited thereto since various modifications may be made, and I contemplate by the appended claims to cover any The such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An adjustable terminating means for a transmission line of the type having an inner conductor and a tubular outer conductor concentric therewith comprising, a pair of plate members having contacting plane surfaces, each of said surfaces having corresponding circular grooves therein, each of said grooves being substantially semi-circular in cross section and said grooves uniting to form a circular passageway between said members, a loop of wire centrally supported in said passageway, one end of said loop being connected to said inner conductor and said members being conductively connected to said tubular outer conductor, said loop cooperating with the walls of said passageway to form a section of concentric transmission line, a shaft concentric with said grooves for rotatably supporting one of said members with respect to the other of said members; and a contact member carried by said one member and slidable along said loop to vary the amount of said section connected in series with said transmission line as said one member is rotated with respect to said other member.

2. A rotary tuning device for a concentric transmission line comprising a stationary body member having a plane surface, a movable member rotatably supported by said bod member, said movable member having a plane surface, means to secure said members together with said plane surfaces in engagement, each of said surfaces having corresponding circular grooves cut therein, said grooves being semi-circular in cross section and uniting to form a circular passageway between said members, a substantially circular loop of conductive material centrally supported in said passageway to form with the walls of said passageway a section of concentric transmission line, said loop being conductively connected to said members at one of its ends and being insulated from said members throughout the remainder if its length, a contact member supported by said movable member, and resilient means for causing said contact member to slide along said loop as said movable member is rotated to adjust the length of said section of transmission line.

3. An adjustable terminating means for a transmission line of the type having an inner conductor and a tubular outer conductor concentric therewith comprising a pair of circular plate members having contacting plane surfaces, one of said members being supported for concentric rotation with respect to the other of said members, each of said surfaces having corresponding circular grooves therein, each of said grooves being substantially semi-circular in cross section and said grooves uniting to form a circular passageway between said members, a loop of wire centrally supported in said passageway, one end of said loop being connected to said inner conductor and said members being conductively connected to said tubular outer conductor, said loop coopcrating with the walls of said passageway to form a. section of concentric transmission line, and a contact member carried by said one member and slidable along said loop to vary the amount of said section connected in series with said transmission line as said one member is rotated with respect to said other member.

HALSEY W. ICLINE. 

